LM2907 Frequency to Voltage Converter

The LM2907, LM2917 series are monolithic frequency to voltage converters with a high gain op amp/comparator designed to operate a relay, lamp, or other load when the input frequency reaches or exceeds a selected rate.

The tachometer uses a charge pump technique and offers frequency doubling for low ripple, full input protection in two versions (LM2907-8, LM2917-8) and its output swings to ground for a zero frequency input.

LM2907 frequency to voltage converter is fully compatible with the tachometer and has a floating transistor as its output. This feature allows either a ground or supply referred load of up to 50 mA. The collector may be taken above VCC up to a maximum VCE of 28V. The two basic configurations offered include an 8-pin device with a ground referenced tachometer input and an internal connection between the tachometer output and the op amp non-inverting input. This version is well suited for single speed or frequency switching or fully buffered frequency to voltage conversion applications.

Features of LM2907

• Ground referenced tachometer input interfaces directly with variable reluctance magnetic pickups

• Op amp/comparator has floating transistor output

• 50 mA sink or source to operate relays, solenoids, meters, or LEDs

• Frequency doubling for low ripple

• Tachometer has built-in hysteresis with either differential input or ground referenced input

• Built-in zener on LM2917

• ±0.3% linearity typical

• Ground referenced tachometer is fully protected from damage due to swings above VCC and below ground

Applications of LM2907

• Over/under speed sensing

• Frequency to voltage conversion (tachometer)

• Speedometers

• Breaker point dwell meters

• Hand-held tachometer

• Speed governors

• Cruise control

• Automotive door lock control

• Clutch control

• Horn control

• Touch or sound switches